Error when attaching a file

I tried to send a secure email using Encyro with an attachment. The Send page responded with an error message. What should I do?

[Error: Upload failed. We could not connected to the Internet or an anti-virus/browser-extension is blocking file uploads. If this persists, please note what you were trying to do and contact us.]

1. Usually, attaching a file (or uploading a file on the Send message page when composing a message) should just work. Sometimes, trying again will resolve the issue if the error was due to temporary network issues (that may have caused the upload connection to break in the middle of an upload).
2. Another reason why uploads fail is if the file size is too large or the upload is taking too long. If you have a fast Internet connection, uploads of files up to about 5GB in size will work. If the connection is slow, you may only be able to upload smaller files because when the file is taking too long, our server may reject it. 
3. A third possibility is that an antivirus, a browser plugin, or a similar software is blocking the upload from your browser. For this case, see why uploading a file fails.